Key Enzyme Needed for Growth, Infection, and Cell Recycling in Rice Disease

Jim Crocker
16th July, 2024

Key Enzyme Needed for Growth, Infection, and Cell Recycling in Rice Disease

Deletion of the MoPYR4 gene severely weakens the pathogenicity of the rice blast fungus (Magnaporthe oryzae), resulting in significantly smaller disease lesions on inoculated barley (Hordeum vulgare) leaves (a, b, d, e) and rice (Oryza sativa) seedlings (c, f).

Image adapted from: Wang et al. / CC BY (Source)

Key Findings

  • Researchers at Zhejiang University studied the role of the MoPyr4 protein in the rice blast fungus, Magnaporthe oryzae
  • Deleting the MoPYR4 gene in the fungus led to poor growth, reduced spore production, and defective infection structures
  • Adding external UMP restored normal growth and infection ability in the MoPYR4-deleted fungus
The study conducted by researchers at Zhejiang University explores the role of Dihydroorotase (DHOase) in the rice blast fungus, Magnaporthe oryzae[1]. DHOase is the third enzyme in the pyrimidine nucleotide de novo biosynthesis pathway, which is essential for the synthesis of DNA and RNA. This pathway is conserved across bacteria and eukaryotes, but its function in plant pathogenic fungi has been relatively unexplored. In their investigation, the researchers identified a homologous protein of DHOase in M. oryzae, named MoPyr4, and examined its impact on fungal growth, pathogenicity, and autophagy. Deletion of the MoPYR4 gene resulted in significant defects in the fungus's growth, spore formation (conidiation), and the development of structures called appressoria, which are essential for infecting plant tissues. Additionally, the deletion mutant showed impaired transfer and degradation of glycogen and lipid droplets, reduced turgor pressure in appressoria, and limited expansion of invasive hyphae, ultimately leading to weakened pathogenicity. The study highlights that the long-term addition of exogenous uridine-5’-phosphate (UMP) could restore the normal phenotype and virulence of the ΔMopyr4 mutant. This finding underscores the importance of MoPyr4 in UMP biosynthesis and its critical role in the development and pathogenicity of M. oryzae. Further analysis revealed that MoPyr4 is involved in several key signaling pathways and stress response mechanisms. It participates in the Pmk1-MAPK signaling pathway, which is crucial for fungal pathogenicity, and co-localizes with peroxisomes to manage oxidative stress. MoPyr4 also plays a role in the Osm1-MAPK signaling pathway, which helps the fungus respond to hyperosmotic stress. Moreover, MoPyr4 interacts with MoAtg5, a core protein involved in autophagy, and positively regulates autophagic degradation. These findings align with previous research on the pyrimidine biosynthetic pathway, which has demonstrated its critical role in various organisms. For instance, the evolutionary analysis of the pyrimidine pathway in eukaryotes has shown a highly mosaic organization, suggesting the importance of horizontal gene transfer and endosymbiosis in its establishment[2]. Additionally, the role of pyrimidine metabolism in cancer progression has been well-documented, with dihydroorotate dehydrogenase (DHODH) being a key target for cancer treatment[3]. The multifunctional protein CAD, which includes DHOase as one of its domains, has also been identified as central to nucleic acid synthesis and various physiological processes[4]. In the context of plant pathogenic fungi, the study of pyrimidine metabolism is relatively new. Previous research on the oomycete Phytophthora infestans, a pathogen causing significant agricultural losses, has highlighted the importance of pyrimidine biosynthesis during different stages of infection[5]. The current study on M. oryzae expands this understanding by demonstrating the critical role of MoPyr4 in fungal development and pathogenicity. In conclusion, the research conducted by Zhejiang University provides valuable insights into the biological function of DHOase in plant pathogenic fungi. By identifying and characterizing MoPyr4 in M. oryzae, the study reveals its essential role in UMP biosynthesis, stress response mechanisms, and pathogenicity. These findings not only enhance our understanding of fungal biology but also open up potential avenues for developing new strategies to combat fungal diseases in crops.

BiotechPlant ScienceMycology

References

Main Study

1) Dihydroorotase MoPyr4 is required for development, pathogenicity, and autophagy in rice blast fungus

Published 15th July, 2024

https://doi.org/10.1186/s12964-024-01741-4

Related Studies

2) Evolutionary implications of the mosaic pyrimidine-biosynthetic pathway in eukaryotes.

Journal: Gene, Issue: Vol 257, Issue 2, Oct 2000

3) Targeting Pyrimidine Metabolism in the Era of Precision Cancer Medicine.

https://doi.org/10.3389/fonc.2021.684961

4) Pyrimidine Biosynthetic Enzyme CAD: Its Function, Regulation, and Diagnostic Potential.

https://doi.org/10.3390/ijms221910253

5) De novo pyrimidine biosynthesis in the oomycete plant pathogen Phytophthora infestans.

https://doi.org/10.1016/j.gene.2013.12.009


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